What is roll center and how does it affect your handling and performance.

In a corner centrifugal force causes your rc car or truck to lean into the corner. The point at which your front suspension pivots on is your front roll point and the same holds true for the rear suspension.

When you draw an imaginary line between these two pivot points is your chassis roll axis.

When determining your roll center you are going to need to remember some geometry.

Because , roll center is the angles of your suspension components, lower control arms (A-arms), and camber links or upper control arms (A-arms), center of gravity and center of your contact patch.

So, it is not easy calculating your roll center. Many full size race teams have a team of engineers working on this full time.

But, with a little practice and patience you can master determining and adjusting your roll center.

Referring to the photo above.

Starting at point "A", the upper and lower control arms outer mounting points draw an imaginary line through point "B" in inner upper and lower control arms mounting point.

Then continue these two lines out till they intersect, point "C". Point "C" is your instant center.

When you change the angle of your upper control arms this will either move your instant center nearer to or farther away from the opposite tire.

The closer you have your instant center to the opposite tire the more negative camber gain you will have in a corner.

To move the instant center closer or farther from the opposite tire is accomplished by either lowering or raising the upper control arms inner mounting position or the outer mounting position.

The closer your instant center is to the opposite tire the more negative camber gain you are going to experience and the less static negative camber you will need to have dialed into your vehicle.

Understanding camber gain and taking full advantage of it can improve both straight line and cornering performance.

It allows you to always have the maximum contact patch on the racing surface. More contact patch translates into more traction.

How camber gain works, as you first enter a corner your suspension has not yet reacted so your negative camber setting initially holds your rc vehicle stable and maintains traction.



As your suspension starts to compress and the chassis starts to lean into the corner your negative camber setting will increase.

This helps to keep your outside tire flat on the surface, while the opposite happens on the inside tire. As your chassis rolls into a corner in inside suspension decompresses reducing negative camber allowing only the inner most of the tire to be in contact with the surface.

Understanding instant center and negative camber gain is very important to monster trucks and truggies, because of their higher center of gravity, longer control arms, large side walled tires and weight.

So, taking advantage of camber gain can result in the best of both worlds only a few degrees of static negative camber for great straight line traction.

While at the same time having a quick negative camber gain entering a corner, for great cornering speed and stability, with the maximum contact patch as possible.

Find the instant center of both your left and right side.

Draw an imaginary line from your instant center, point "C", to the center of the contact patch of that tire, point "D".

Where the lines intersect from the instant center to the center of the contact patch is the roll center for that portion of your suspension, point "E".

Repeat for the other end of your vehicle. The imaginary line through the front and rear roll centers is your roll axis.

Referring to the photo below.

The important part of understanding your roll center is your momentum arm.

This is the line from your center of gravity to your roll center. This line will increase or decrease as you change your ride height.

As you raise your ride so will your momentum arm increase. This will also increase your chassis roll in a corner.

While lowering your ride height will decrease your momentum arm and decrease chassis roll.

With all the variables in adjusting and tuning your suspension there are no hard and fast rules as to just how this is going to affect your rc vehicle.

It is some thing that you will just need to play with to both suit your driving style and conditions.

Just remember that roll center, instant center and momentum arm are all related and have subtle effects.

As you get closer to getting your rc vehicle "dialed-in" for conditions playing with or changing roll center and instant center could just add that little advantage you are looking for.

With there being some many different adjustments on almost all rc vehicles that are easier and have bigger results leave any tweaking to roll center and instant center to one of the last fine tuning points.

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